Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756740Ab2BGJD2 (ORCPT ); Tue, 7 Feb 2012 04:03:28 -0500 Received: from mail-qy0-f174.google.com ([209.85.216.174]:36698 "EHLO mail-qy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756705Ab2BGJDT (ORCPT ); Tue, 7 Feb 2012 04:03:19 -0500 Date: Tue, 7 Feb 2012 17:03:05 +0800 From: Yong Zhang To: =?utf-8?B?PT91dGYtOD9RP0xvdGhhcl9XYT1DMz05Rm1hbm4/PQ==?= Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Thomas Gleixner Subject: Re: [BUG] genirq: Race condition in ONESHOT IRQ handler disabling IRQ forever Message-ID: <20120207090305.GB32736@zhy> Reply-To: Yong Zhang References: <20271.35831.227679.177366@ipc1.ka-ro> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20271.35831.227679.177366@ipc1.ka-ro> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3034 Lines: 81 On Mon, Feb 06, 2012 at 09:14:47AM +0100, =?utf-8?Q?Lothar_Wa=C3=9Fmann?= wrote: > Hi, > > I already sent this to on Feb. 1, 2012 > but did not get any response there. So resending to a wider audience > with improved subject line: > > there is a race condition in the threaded IRQ handler code for oneshot > interrupts that may lead to disabling an IRQ indefinitely. IRQs are > masked before calling the hard-irq handler and are unmasked only after > the soft-irq handler has been run. Thus if the hard-irq handler > returns IRQ_HANDLED instead of IRQ_WAKE_THREAD, meaning the soft-irq > will not be called, the interrupt will remain masked forever. > > This can happen due to a short pulse on the interrupt line, that > triggers the interrupt logic, but goes undetected by the hard-irq > handler. The problem can be reproduced with the TSC2007 touch > controller driver that uses ONESHOT interrupts. Isn't it the responsibility of the driver (say TSC2007)? In this case, TSC2007 should return IRQ_WAKE_THREAD IMHO. Thanks, Yong > > The problem arises also with interrupt controllers that latch a level > triggered IRQ until it is acknowledged (like the i.MX28 does). > In this case the IRQ status bit will remain asserted after the > soft-irq finishes and retrigger the interrupt while the interrupt line > is already deasserted. > > The following patch would solve the problem, but I'm not sure whether > it's the Right Thing(TM) to do. Especially wrt. shared interrupts. > > diff --git a/kernel/irq/handle.c b/kernel/irq/handle.c > index 470d08c..93beadb 100644 > --- a/kernel/irq/handle.c > +++ b/kernel/irq/handle.c > @@ -146,6 +146,11 @@ handle_irq_event_percpu(struct irq_desc *desc, struct irqaction *action) > /* Fall through to add to randomness */ > case IRQ_HANDLED: > random |= action->flags; > + /* unmask the IRQ that has been left masked > + * due to race condition > + */ > + if (res == IRQ_HANDLED && (action->flags & IRQF_ONESHOT)) > + unmask_irq(desc); > break; > > default: > > Best regards, > > Lothar Wassmann > -- > ___________________________________________________________ > > Ka-Ro electronics GmbH | Pascalstraße 22 | D - 52076 Aachen > Phone: +49 2408 1402-0 | Fax: +49 2408 1402-10 > Geschäftsführer: Matthias Kaussen > Handelsregistereintrag: Amtsgericht Aachen, HRB 4996 > > www.karo-electronics.de | info@karo-electronics.de > ___________________________________________________________ > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- Only stand for myself -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/